// solution/author-4-29.cpp
// {
// "verdict": "partially_correct",
// "except": {
// "samples": "correct",
// "from_root": "correct"
// }
// }
// END HEADER
// ********************************************************
// ** Solution of Z = 4 with 29 writes
// ********************************************************
#include <bits/stdc++.h>
#include "migrations.h"
using namespace std;
// variables for ahmed
namespace device {
int N, B;
vector<int> p;
int u, v;
int ubase, vbase, cur;
// initialization
void init(int N_) {
N = N_;
B = int(ceil(log2(N)));
p = { -1 };
u = 0; v = 0;
ubase = 0; vbase = 0; cur = 0;
}
// calculate distance
int dist(int x, int y) {
int d = 0;
while (x != y) {
if (x > y) {
x = p[x];
}
else {
y = p[y];
}
d += 1;
}
return d;
}
// function for ahmed
int ahmed(int t, int parent) {
// step #1. preparation
p.push_back(parent);
int d1 = dist(u, v);
int d2 = dist(u, t);
int d3 = dist(v, t);
int pattern;
if (d1 >= d2 && d1 >= d3) {
pattern = 0; // Pattern A
}
else if (d1 <= d2 && d2 >= d3) {
v = t;
pattern = 1; // Pattern B
}
else {
u = v;
v = t;
pattern = 2; // Pattern C
}
if (t == N - (B * 2 + 1) - 1) {
ubase = u;
vbase = v;
}
// step #2. if pre-writing phase, don't write
if (t < N - (B * 2 + 1)) {
return 0;
}
// step #3. writing phase
if (pattern == 2) {
return 4;
}
int bit = (cur < B ? (ubase >> cur) & 1 : (cur < 2 * B ? (vbase >> (cur - B)) & 1 : 0));
cur += 1;
return pattern * 2 + bit;
}
}
// dummy function for ahmed
int send_message(int N, int pos, int P) {
if (pos == 1) {
device::init(N);
}
int res = device::ahmed(pos, P);
return res;
}
// function for hassan
std::pair<int, int> longest_path(vector<int> Cards) {
// step #1. preparation
int N = Cards.size();
int B = int(ceil(log2(N)));
// step #2. decoding of (u, v) in pre-writing phase
int ubase = 0, vbase = 0, cur = 0;
for (int t = max(N - (2 * B + 1), 1); t < N && cur < 2 * B; t++) {
if (Cards[t] != 4) {
int bit = (Cards[t] & 1);
if (cur < B) {
ubase += bit << cur;
}
else {
vbase += bit << (cur - B);
}
cur += 1;
}
}
// step #3. decode patterns
int u = ubase, v = vbase;
for (int t = max(N - (2 * B + 1), 1); t < N; t++) {
int pattern = Cards[t] / 2;
if (pattern == 1) {
v = t; // Pattern B
}
if (pattern == 2) {
u = v;
v = t; // Pattern C
}
}
return make_pair(u, v);
}
